Commentary on the Supreme Court often sounds like a sportscaster announcing a close game between well-known rivals: "The liberals and conservatives are tied going into the bottom of the ninth. Sonia Sotomayor, a promising rookie, is coming in to relieve Souter, but they are both so similar, it won't matter. At bat is the streaky Anthony Kennedy. When he's hot, the conservatives win, but if he's slumping, the liberals can squeeze by."

This kind of play-by-play captures two important realities about the court. Many decisions are sharply divided between two equal and predictable blocs, with Kennedy providing the decisive vote. And the conventional labels of "liberal" and "conservative" do describe the ideological backgrounds of most of the justices in each bloc before they joined the court. (David H. Souter and John Paul Stevens, moderate Republicans appointed by Republican presidents, are the exceptions.)

Nevertheless, the obsession with a crude and easy liberal/conservative dichotomy in the media and in the Senate hearing room impedes a sophisticated public understanding of judicial process and the law. It conceals more than it reveals. First, it obscures the fact that the cases the court hears are all very hard, almost by definition, with excellent legal arguments (not just ideological ones) on both sides. Except for direct appeals from state supreme courts, the court primarily accepts cases in which the federal circuit courts, operating with the same facts and legal materials, nonetheless reached opposite conclusions.

Second, the specific facts of a case are often pivotal to the legal analysis and to the future reach of any judicial decision. Yet the media and the politicians ignore the details, preferring the drama of a Manichean liberal/conservative battle for legal supremacy.

Third, the commentary suggests that the justices are free agents who can simply choose the results they favor. In reality, they are substantially constrained by legal rules -- precedents within which they must work. Also, the applicable statute or other legal text uses certain words and not others, and also carries a specific legislative and administrative history, which all must be interpreted. More than one interpretation is possible in hard cases, of course, but constraining interpretive traditions make some readings more persuasive than others. Finally, technical doctrines, such as the duty to interpret statutes in ways that will avoid constitutional rulings, also limit what courts may do.

Let me be clear: These constraints do not dictate the outcome in hard cases. Any good lawyer can argue the plausibility of competing precedents and interpretations, the plasticity of legal doctrines and different ways of viewing the same facts -- and these arguments create openings that judges can and do exploit to reach a preferred outcome. My point, rather, is that these constraints significantly limit justices' discretion, and the justices take them seriously. The pundits seldom do.

The recent Ricci decision upholding a reverse discrimination claim by a white New Haven firefighter illustrates these points. It was certainly a hard case, as the 5-4 decision suggests. What captured the headlines and media commentary was the court's split along familiar liberal/conservative lines. But this ideological story line obscures much that the public needs to know.

The city had administered a written test to determine which firefighters would be promoted. What mattered most to the decision was how the justices viewed the evidence on the suitability of the test, the reasons New Haven's officials decided to jettison the test results after minorities failed it and the probability of a successful civil rights suit against the city by those minority firefighters had the city certified the results. The court made subtle, fact-based distinctions among different approaches to affirmative action in deciding how much burden particular individuals or groups should have to bear.

You'll hear little about these details during the confirmation hearings when the case comes up (Sotomayor was on the lower court whose decision the Supreme Court overturned). Do not expect the media or the senators to mention the important fact that eight of the justices, liberal and conservative alike, actually agreed that the city had applied the wrong legal standard. All they seem to care about is that the conservatives carried the day.

The monomania about the justices' ideological leanings has a number of perverse effects. It hides, indeed denies, the fascinating interplay among legal doctrine, textual interpretation and the factual record in determining outcomes. The left/right story line also crowds out the much more revealing lawyerly divisions among the justices about what should matter in resolving hard cases. What really divides the justices is the relative importance of national uniformity in law versus local diversity, of clear rules versus more contextual standards, of state authority versus individual rights, of deference to elected officials or to bureaucratic expertise, of the default rules for interpreting ambiguous language and so forth.

Indeed, ideological labels are misleading even in their own terms. Real people and real judges mix liberalism on some issues with conservatism on others. For example, the very conservative Antonin Scalia voted with liberals to uphold punitive jury awards against product manufacturers -- the position advocated by the trial lawyers, a leading Democratic lobby -- because he thinks the Constitution permits such awards. The labels also reveal little about the values underlying them. For example, is a "law-and-order conservative" callous toward the life challenges faced by poor people, or instead sensitive to the depredations of crime on the poor? Is a "social policy liberal" an advocate of state-mandated redistribution, or instead a believer in state-enforced equal opportunity?

As the Sotomayor hearings proceed, much of the questioning and the media coverage will describe the nominee in crude ideological terms. But if you listen carefully as she explains her reasoning, you will hear a good legal mind at work, one that defies those too-convenient categories. In the end, her lawyerly skills will determine her fitness for and her potential legacy on the court.

Peter H. Schuck, a Yale Law School professor, is co-editor (with James Q. Wilson) of "Understanding America: The Anatomy of an Exceptional Nation."